The present invention relates to ink jet printing and in particular discloses a shape memory alloy ink jet printer.
The present invention further relates to the field of drop on demand ink jet printing.
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Ink Jet printers themselves come in many different types. The utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)
Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Manufacturers such as Canon and Hewlett Packard manufacture printing devices utilizing the electro-thermal actuator.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high-speed operation, safe and continuous long-term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
It is an object of the present invention to provide for a new form of ink jet printing device that utilizes a shape memory alloy in its activation method.
In accordance with a first aspect of the present invention there is provided a method of ejecting ink from a chamber comprising the steps of: a) providing a cantilevered beam actuator incorporating a shape memory alloy; and b) transforming said shape memory alloy from its martensitic phase to its austenitic phase or vice versa to cause the ink to eject from said chamber. Further, the actuator comprises a conductive shape memory alloy panel in a quiescent state and which transfers to an ink ejection state upon heating thereby causing said ink ejection from the chamber. Preferably, the heating occurs by means of passing a current through the shape memory alloy. The chamber is formed from a crystallographic etch of a silicon wafer so as to have one surface of the chamber substantially formed by the actuator. Advantageously, the actuator is formed from a conductive shape memory alloy arranged in a serpentine form and is attached to one wall of the chamber opposite a nozzle port from which ink is ejected. Further, the back etching of a silicon wafer to the epitaxial layer and etching a nozzle porthole in the epitaxial layer forms the nozzle port. The crystallographic etch includes providing side wall slots of non-etched layers of a processed silicon wafer so as to extend the dimensions of the chamber as a result of the crystallographic etch process. Preferably, the shape memory alloy comprises nickel titanium alloy.
By way of background, reference is made to U.S. patent application Ser. No. 09/113,097 by the applicant. It is an object of the invention of that application to provide an alternative form of drop on demand ink jet printing utilising a reverse spring lever arrangement to actuate the ejection of ink from a nozzle chamber.
In accordance with a first aspect of that invention, there is provided an ink jet printing nozzle apparatus with a connected ink supply chamber, the apparatus comprising an ink ejection means having one surface in fluid communication with the ink in the nozzle chamber, a recoil means connected to the ink ejection means and a first actuator means connected to the ink ejection means. The method of ejecting ink from the ink chamber comprises the steps of activation of the first actuator means which drives the ink ejection means from a quiescent position to a pre-firing position and deactivation of the first actuator means, causing the recoil means to drive the ink ejection means to eject ink from the nozzle chamber through the ink ejection port. Further, the recoil means includes a resilient member and the movement of the first actuator results in resilient movement of this recoil means and the driving of the ink ejection means comprises the resilient member acting upon the ink ejection means. Preferably, the first actuator means comprises an electromagnetic actuator and the recoil means comprises a torsional spring. The ink ejection means and the first actuator are interconnected in a cantilever arrangement wherein small movements of the first actuator means result in larger movements of the ink ejection means. Advantageously, the recoil means is located substantially at the pivot point of the cantilever construction. The first actuator includes a solenoid coil surrounded by a magnetic actuator having a first mixed magnetic pole and a second moveable magnetic pole, such that, upon activation of the coil, the poles undergo movement relative to one another with the moveable magnetic pole being connected to the actuator side of the cantilever construction. Preferably, the moveable magnetic pole includes a plurality of slots for the flow of ink through the pole upon movement. The ink ejection means comprises a piston or plunger having a surface substantially mating with at least one surface of the nozzle chamber.
Also by way of background, reference is made to U.S. patent application Ser. No. 09/113,061 by the applicant. It is an object of the invention of that application to provide for an alternative form of ink jet printer which uses a linear stepper actuator to eject ink from a nozzle chamber.
In accordance with a first aspect of that invention, an ink jet nozzle arrangement is presented comprising: a nozzle chamber having an ink ejection port for the ejection of ink, an ink supply reservoir for supplying ink to the nozzle chamber, a plunger located within the nozzle chamber and further, a linear stepper actuator interconnected to the plunger and adapted to actuate the plunger so as to cause the ejection of ink from the ink ejection port. At least one surface of the plunger located alongside a wall of the nozzle chamber is hydrophobic. Preferably, the linear actuator interconnected to the plunger in the nozzle chamber is driven in three phases by a series of electromagnets. Preferably, a series of twelve electromagnets is arranged in opposing pairs alongside the linear actuator. Further, each phase is duplicated resulting in four electromagnets for each phase. The ink jet nozzle has an open wall along a back surface of the plunger which comprises a series of posts adapted to form a filter to filter ink flowing through the open wall into the nozzle chamber. The linear actuator construction includes a guide at the end opposite to the nozzle chamber for guiding the linear actuator.